Contextual novelty changes reward representations in the striatum

Reward representation in ventral striatum is boosted by perceptual novelty, although the mechanism of this effect remains elusive. Animal studies indicate a functional loop (Lisman and Grace, 2005) that includes hippocampus, ventral striatum, and midbrain as being important in regulating salience attribution within the context of novel stimuli. According to this model, reward responses in ventral striatum or midbrain should be enhanced in the context of novelty even if reward and novelty constitute unrelated, independent events. Using fMRI, we show that trials with reward-predictive cues and subsequent outcomes elicit higher responses in the striatum if preceded by an unrelated novel picture, indicating that reward representation is enhanced in the context of novelty. Notably, this effect was observed solely when reward occurrence, and hence reward-related salience, was low. These findings support a view that contextual novelty enhances neural responses underlying reward representation in the striatum and concur with the effects of novelty processing as predicted by the model of Lisman and Grace (2005)

Leptophobic Z' from superstring derived models

It was recently suggested that the reported anomalies in R_b and R_c can be interpreted as the effect of a heavy vector boson that couples to quarks and is universally decoupled from leptons. We examine how an extra gauge boson with this property can arise from superstring derived models. In a specific three generation model we show that the U(1)_{B-L} symmetry combines with the horizontal flavor symmetries to form a universal leptophobic U(1) symmetry. In our model there is an enhancement of the color gauge group from twisted sectors. The enhancement occurs after the breaking of the unifying gauge symmetry by ``Wilson lines''. The leptophobic U(1) symmetry then becomes a generator of the color SU(4) gauge group. We examine how similar symmetries may appear in other string models without the enhancement. We propose that if the current LEP anomalies persist it may be evidence for a certain class of un--unified superstring models

Dopamine restores reward prediction errors in old age.

Senescence affects the ability to utilize information about the likelihood of rewards for optimal decision-making. Using functional magnetic resonance imaging in humans, we found that healthy older adults had an abnormal signature of expected value, resulting in an incomplete reward prediction error (RPE) signal in the nucleus accumbens, a brain region that receives rich input projections from substantia nigra/ventral tegmental area (SN/VTA) dopaminergic neurons. Structural connectivity between SN/VTA and striatum, measured by diffusion tensor imaging, was tightly coupled to inter-individual differences in the expression of this expected reward value signal. The dopamine precursor levodopa (L-DOPA) increased the task-based learning rate and task performance in some older adults to the level of young adults. This drug effect was linked to restoration of a canonical neural RPE. Our results identify a neurochemical signature underlying abnormal reward processing in older adults and indicate that this can be modulated by L-DOPA

Osteoquimionecrosis de los maxilares asociada a la administración de bifosfonatos por vía endovenosa: a propósito de seis casos

La osteonecrosis de los maxilares en pacientes con cáncer se asociaba, hasta ahora, con la radioterapia, aunque recientemente se han reportado numerosos casos de osteoquimionecrosis de los maxilares (OQNM) relacionada con la quimioterapia, y más concretamente con el uso de los bifosfonatos (agentes inhibidores de la actividad osteoclástica), utilizados para el tratamiento de las metástasis óseas. Los bifosfonatos inhiben la actividad osteoclástica dando lugar a una disminución de la reabsorción y la remodelación del hueso, comprometiendo su irrigación. Si bien la disminución del aporte vascular en el hueso podría presentarse en cualquier localización, parece lógico que en la mayoría de los casos afecte a los huesos maxilares debido a que su vascularización es de tipo terminal, y al hecho de que es un hueso expuesto a agresiones del medio exterior, ya sea a través del periodonto o del conducto radicular. Se presentan las complicaciones observadas en 6 casos de OQNM desencadenadas tras la ejecución de diversas terapias quirúrgicas bucales en pacientes sometidos a un tratamiento con bifosfonatos por diferentes patologías y su manejo terapéutico. El tratamiento de este tipo de OQNM suele ser insatisfactorio, ya que ninguna de las opciones terapéuticas descritas en la literatura ha obtenido buenos resultados. Todos los pacientes que van a recibir o han recibido tratamiento con bifosfonatos deben ser considerados como pacientes de riesgo de OQNM, y deben someterse a las mismas medidas profilácticas descritas para la prevención de la osteorradionecrosis

High-speed tunable photonic crystal fiber-based femtosecond soliton source without dispersion pre-compensation

We present a high-speed wavelength tunable photonic crystal fiber-based source capable of generating tunable femtosecond solitons in the infrared region. Through measurements and numerical simulation, we show that both the pulsewidth and the spectral width of the output pulses remain nearly constant over the entire tuning range from 860 to 1160 nm. This remarkable behavior is observed even when pump pulses are heavily chirped (7400 fs^2), which allows to avoid bulky compensation optics, or the use of another fiber, for dispersion compensation usually required by the tuning device.Comment: 8 pages, 11 figure

Synchronization of medial temporal lobe and prefrontal rhythms in human decision-making

Optimal decision making requires that we integrate mnemonic information regarding previous decisions with value signals that entail likely rewards and punishments. The fact that memory and value signals appear to be coded by segregated brain regions, the hippocampus in the case of memory and sectors of prefrontal cortex in the case of value, raises the question as to how they are integrated during human decision making. Using magnetoencephalography to study healthy human participants, we show increased theta oscillations over frontal and temporal sensors during nonspatial decisions based on memories from previous trials. Using source reconstruction we found that the medial temporal lobe (MTL), in a location compatible with the anterior hippocampus, and the anterior cingulate cortex in the medial wall of the frontal lobe are the source of this increased theta power. Moreover, we observed a correlation between theta power in the MTL source and behavioral performance in decision making, supporting a role for MTL theta oscillations in decision-making performance. These MTL theta oscillations were synchronized with several prefrontal sources, including lateral superior frontal gyrus, dorsal anterior cingulate gyrus, and medial frontopolar cortex. There was no relationship between the strength of synchronization and the expected value of choices. Our results indicate a mnemonic guidance of human decision making, beyond anticipation of expected reward, is supported by hippocampal–prefrontal theta synchronization

TeV Strings and the Neutrino-Nucleon Cross Section at Ultra-high Energies

In scenarios with the fundamental unification scale at the TeV one expects string excitations of the standard model fields at accessible energies. We study the neutrino-nucleon cross section in these models. We show that duality of the scattering amplitude forces the existence of a tower of massive leptoquarks that mediate the process in the s-channel. Using the narrow-width approximation we find a sum rule for the production rate of resonances with different spin at each mass level. We show that these contributions can increase substantially the standard model neutrino-nucleon cross section, although seem insufficient in order to explain the cosmic ray events above the GZK cutoff energy.Comment: 10 pages, 1 figure, version to appear in PR

The effects of non-universal extra dimensions on the radiative lepton flavor decays \mu\to e\gamma and \tau\to \mu\gamma in the two Higgs doublet model

We study the effect of non-universal extra dimensions on the branching ratios of the lepton flavor violating processes \mu\to e\gamma and \tau\to \mu\gamma in the general two Higgs doublet model. We observe that these effects are small for a single extra dimension, however, in the case of two extra dimensions there is a considerable enhancement in the additional contributions.Comment: 16 Pages, 9 Figure

Higgs bosons in the simplest SUSY models

Nowadays in the MSSM the moderate values of $\tan\beta$ are almost excluded by LEP II lower bound on the lightest Higgs boson mass. In the Next-to-Minimal Supersymmetric Standard Model the theoretical upper bound on it increases and reaches maximal value in the strong Yukawa coupling limit when all solutions of renormalization group equations are concentrated near the quasi-fixed point. For calculation of Higgs boson spectrum the perturbation theory method can be applied. We investigate the particle spectrum in the framework of the modified NMSSM which leads to the self-consistent solution in the strong Yukawa coupling limit. This model allows one to get $m_h\sim 125$ GeV at values of $\tan\beta\ge 1.9$. In the investigated model the lightest Higgs boson mass does not exceed $130.5\pm 3.5$ GeV. The upper bound on the lightest CP-even Higgs boson mass in more complicated supersymmetric models is also discussed.Comment: 27 pages, 5 figures included, LaTeX 2e. Plenary talk at the Conference of RAS Nuclear Physics Department 2000 in ITEP, Moscow, Russia; to appear in Phys. Atom. Nuc

Practical approach on frail older patients attended for acute heart failure

Acute heart failure (AHF) is a multi-organ dysfunction syndrome. In addition to known cardiac dysfunction, non-cardiac comorbidity, frailty and disability are independent risk factors of mortality, morbidity, cognitive and functional decline, and risk of institutionalization. Frailty, a treatable and potential reversible syndrome very common in older patients with AHF, increases the risk of disability and other adverse health outcomes. This position paper highlights the need to identify frailty in order to improve prognosis, the risk-benefits of invasive diagnostic and therapeutic procedures, and the definition of older-person-centered and integrated care plans